Permanent lifting magnet



May 16, 1944. J, D BY 2,348,967

PERMANENT LIFTING MAGNET Filed D60. 8, 1941 nun!!! /6 IHHHHH INVENTOR. CAAPENCE I DUE) BY ,z/Al v 404% A TC L AED Patented M116, 1944 UNITED STATES PATENT OFFICE PERMANENT LIFTING MAGNET Clarence J. Duby, Youngstown, Ohio I Application December 8, 1941,Serial No. 422,087

B-Claims. (Cl. 175367) This invention relates to lifting magnets, and more particularlyto a lifting magnet employing a permanent magnet.

Lifting magnets are generally of the so-called electromagnet type. I This type of magnet usually comprises a hollow shell formed to provide a pair of poles, usually a center pole which is surrounded by a concentric outer pole. A magnet winding is disposed between the two poles and around the center pole which winding is operated by causing a heavy. direct currentto flow through the winding which causes the poles to be magnetized. the current usually being applied after the magnet is lowered in contact with the load. After; the magnet is energized the load may be pickedup and transported from place to place. the load being held by the magnet so long as it is energized. If for some reason a power failureoccurs, the load may be dropped. This provides a potential safety hazard since power failure may occur at any unforeseen time and when it does occur the load may be dropped onto persons, machinery, products, or other equipment underneath it, damaging the same and even resulting in the loss of life.

' The present invention contemplates constructing of a magnet of materials of-the so-called permanent magnet type, which materials retain their magnetism after the magnetising force is removed; hence a power failure has substantially no effect upon the lifting or load retaining properties of the magnet. This not only decreases the amount of power needed since the magnet is,

capable of operating when the power is off, but also eliminates the hazard from the dropping of material in event of accidental power failure.

It is, therefore, an object of this invention to I provide a lifting magnet wherein the possibilities of accidental release of the materials carried thereby due to power failure is substantially eliminated.

Another object of the'invention is to provide a lifting magnet wherein the amount of power consumption during use is decreased. 1

Another. object is the provision of a lifting magnet of the permanent magnet type.

Another object of the invention is the provision of an improved method of releasing the load from a permanent magnet type of lifting'r'na'gnet.

Still other objects of the invention and the invention itself will become more apparent from the following description of an embodiment thereof, which description is illustrated by the accompanying drawing. Although the drawing illustrates a circular magnet, it will be apparent that the structure can be applied to magnets of noncircular shape.

In the-drawing:

Fig.1 is a vertical medial section through a magnet constructed according to my invention: -Fig. 2 is a diagram indicating the circuit for operating the magnet.

Referring now to the drawing throughout which like parts have been designated by like reference characters, and particularly Fig. 1, the'magnet comprises a hollow outer case i which may be of cast steel construction provided with integrally formed apertured ears! on its upper side adapted for attachment to a crane cable, hook, or the like. The housing I, as best shown in Fig. 1, is formed to provide a downwardly extending circumferential wall and a center wall coaxial therewith to provide a toroidal space therebetween. This space is in the main filled with aninsert of per.- manent magnet material I, which material may be of an aluminum-nickel-lron alloy known under the trade name of Alnico.

The Alnico is shaped .exteriorly to conform closely to the interior formation of the. shell l which protects and supports it. The Alnicol' insert is also provided with a toroidal space for receiving a winding 9. There is thus provided a ring-shaped outer pole comprising the steel shell and Alnicol" and a coaxialinner pole. The winding 9, whichv may be of toroidal shape is enclosedin a suitable protective material 3 which is non-magnetic and which supports it in and insulates it from the permanent magnet material 6. Openings 30 and 3| extend through the permanent magnet material and jacket "I respectively. Leads II which connect to the winding extend upward through the insulating material and through the plug 32 which closes the ppening 3|. Shoes 4 may be welded or otherwise secured to the poles to provide a protection therefor and to hold the parts in position. The space intermediate the poles in the face of the magnet may be filled-with a suitable protecting filler block indicated at H) and preferably of non-magnetic material.

In operation the Alnico may be permanently magnetized and when so magnetized and brought in contact with any magnetic material the magnetic material adheres firmly to the poles and may be carried from place to place. The winding 5 and its associated circuit is arranged so as to enable a magnetic flux to be generated thereby.

manent magnetic flux of the "Alnico" whereby the permanent magnet properties may be neu tralized to permit dropping of the load. Circuit provisions are also provided whereby the polarity of the winding may be reversed so that the flux generated by the winding operates in conjunction with the permanent magnet to increase the magnetism as well as to offset any residual opposed magnetism which was caused by the current flowing through the-winding in a direction to cause an opposing flux, when the magnet is reconditioned for picking up a load. The winding also can be used to initially magnetize or remagnetize the permanent magnet.

The circuit for accomplishing the foregoing result is best shown in Fig. 2. In this circuit the lines IBD and ISC provide the connection to a source of current which, as previously stated, is a D. C. source. A single pole double throw switch indicated generally at it is provided having the center or movable pole connected to the line ISD and arranged to be moved to either the contact 11 or II which movement connects selectively operating coils I! or across the D. C. line. The coils I 8 and II are provided with suitable armatures which are of well known construction and which armatures are arranged to. selectively operate the contacts HA, H8 and the contacts 22A and 22B.

When the switch blade of the switch it is thrown to the up" position the coil i9 is connected across the line, this causes the contacts 1 IA and MB to be closed; current then flows from the positive side.of the line through the contact IIA downward through the winding 9 and through the contact 2 IB and the adjustable resistance and thence to the negative side of the line. The flux in the coil 9 will be of the correct polarity to assist the permanent magnetmaterial and to magnetize the same. After the magnet is once energized the switch blade may be moved to the intermediate neutral position as illustrated,

the permanent magnet retains its flux which is sumcient to provide the necessary lifting power to retain the material being transported.

When it is desired to release the load the center pole ofthe switch it is moved to the contact l8 which causes the winding 20 to be energized'operating the contacts 22A and 223. It will thus be seen that current flow is from the positive side of the line through the contacts 22A upward through the winding 9 (in a reverse direction to the previous direction) through the contacts 223 and by way of the variable resistance 26 to the negative side of the line. The winding 9 thus being energized by current flowing in the opposite direction which energization is sufiicient to reduce the flux of the magnet to a value low enough to cause the load to be released.

The resistances 25 and 26 being variable can be adjusted to provide the desired operating characteristics, that is sufficient current through the winding! in either direction to fulfill the operations just described. This has a decided advantage inthat when loads of a certain predetermined fixed weight are being ra sed the reversing current can be adjusted to be sufiicient to reduce the magnetic flux so that the load is dropped thus conserving the magnetic flux in the Alnico.

It will be seen that by this construction the disadvantage inherent in the use of previous permanent magnet in the use of mechanical means for eliminating the holding flux is e iminated. In a magnet of the character described it would be extremely difficult and impractical to provide mechanical means for releasing the permanent magnet but by this structure the release is accomplished as easily as in the previous electromagnets. Since the holding flux is due to permanent magnet structure, a power failure will not result in accidental dropping of the load because with the power off the magnetic flux of the permanent magnet is sumcient to hold the contemplated load. Also it will be seen that once the load is picked up it is not necessary to use the power from the line any longer, therefore there is a considerable conservation of electricity because the load is held without the use of a current.

Although I have shown and described a two pole magnet of the concentric pole structure, it is quite within the purview of my invention to provide a multiple pole magnet which can vary in size and conformation and number of poles.

Having thus described my invention I am aware that numerous and extensive departures may be made therefrom without departing from the spirit or scope of the appended claims.

I claim:

1. A lifting magnet construction for lifting loads of diii'erentweight and size comprising a body having poles of opposite polarity extending therefrom, said body being comprised of a material having high magnetic fiux retentivity, a winding cooperating with the poles of said body and circuit means for directing a current through said winding and selectively arranged to direct the current to oppose the magnetic flux in the body and assist, the magnetic flux in the body, the normal magnetic flux of said body being sufficient to retain a load upon cessation of current through said windings.

2. A lifting magnet comprising an outer shell of magnetic material and a filler of high magnetic flux retentivity disposed in the shell. said shell V and filler being formed to provide magnetic poles of opposite polarity, a winding disposed in cooperative relation with said poles, means for directing current through said winding including a switch arranged to selectively direct the current through the winding in opposite directions to energize the winding to magnetize the permanent magnet structure in one position and to act in opposition to the permanent magnet structure in the other position the flux retentivity of said filler being sufficient to hold a load without current in said windings.

-3. A lifting magnet comprising an outer shell of magnetic material, and a filler of high magnetic flux retentivity disposed in the shell, said shell and filler being formed to provide magnetic poles of opposite polarity and a space between said poles for receiving a winding disposed in cooperative relationwith said poles, means for directing current through said winding including a switch arranged to selectively direct the current through the winding. in opposite directions to energize the winding to magnet-ize the permanent magnet structure in one position and to act in opposition to the permanent magnet structure in the other position, adjustable resistance means interposed in said circuit to control the amount of current flowing through said winding.

4. A lifting magnet comprising an outer shell of magnetic material, and a filler of high magnetic flux retentivity disposed in the shell. said shell and filler being formed to provide magnetic poles of opposite polarity and a space between said poles for receiving a winding disposed in cooperswitch arranged to selectively direct the current through the winding in opposite directions to energize the winding to magnetize the permanent magnet structure in one position and to act in opposition to the permanent magnet structure in the other position, adjustable resistance means interposed in said circuit to control the amount of current flowing through said winding in either direction.

5. A lifting magnet comprising a permanent magnet of Alnico formed to provide poles of opposite polarity and a space between said pole pieces, a protective housing surrounding said "Alnico, a winding supported by said protective housing in said space, a circuit controller for controlling flow oi current through said winding, said circuit controller arranged to direct the current through the winding to assist the flux of the permanent magnet and to magnetize the permanent magnet to provide a permanent flux and to oppose the flux of the "Alnico" to reduce the effective flux sufliciently to release a load.

6. A magnet suitable for lifting and transporting magnetic articles 01 varying size, shape and weight, comprising an outer permeable shell, an annular core of high magnetic flux retentivity in said shell, supported and protected thereby, said shell and core being formed to provide concentric magnetic poles of opposite polarity, said core being formed to provide an annular channel and a winding disposed therein, permeable face plates for said shell and for holdin said core and winding therein, and means connecting a source of current to said winding and to control the current to said winding to magnetize the core and to reverse and determine the current in the winding to the point where the flux caused by the current in the winding opposes that of the core fiux sumcient to release a load without permanent loss of flux in the core.

CLARENCE J. DUBY. 

